DESIDERATA^ ETC. 
XXXV 
along which it is high-water at the same instant,) will be dis¬ 
covered. It would be very desirable for those who have the op¬ 
portunity, to combine, so as to effect the detailed description of 
the tides through some small extent of coast, such as that which 
has been effected by M. Daussy for the west coast of France. 
DIRECTIONS FOR OBSERVING THE AURORA 
BOREALIS. 
Notwithstanding the attention which has been paid to the 
phenomena of the Aurora Borealis, and the various hypotheses 
which have been imagined to explain them, it will be found that 
there is a want of information on the points which are most 
necessary as bases of induction ; and the British Association 
have therefore been induced to appoint a Committee in the ex¬ 
press view of directing observers to the really important features 
of this meteor, and of obtaining, by a system of contempo¬ 
raneous observation, data which experience shows cannot be 
derived from insulated exertion. 
The following are the most important points which demand 
the attention of observers : 
1. The elevation of the auroral arches and streamers above 
the surface of the earth. 
2. The determination of the question whether the auroral ex¬ 
hibition is accompanied by sound. 
3. The existence of recurring periods of frequency and 
brilliancy in the Aurora. 
4. The influence of arches, streamers, and other auroral phae- 
nomena upon the magnetic needle. 
1. It is recommended to all who intend to observe auroras 
to make themselves well acquainted with the names of all the 
principal stars to the north of the equator, especially those 
which do not set here. This will be most easily done by study¬ 
ing a celestial globe. Good maps of the stars may also be con¬ 
sulted with advantage. Either the proper names or the Greek 
characters with the name of the constellation will be sufficient. 
Persons who may prefer to determine the angular elevation 
and position of the arches and streamers by graduated instru¬ 
ments, must be supposed well accustomed to the use of them; 
they may, however, be reminded that telescopic sights are for 
this purpose useless, and that steady instruments, which can be 
handled with ease and expedition, are much more available for 
